DE102010001951A1 - Reduction of graphene oxide to graphene in high boiling solvents - Google Patents

Abstract

A method for producing graphene, comprising the steps of dispersing graphene oxide in water to form a dispersion, the method further comprising adding a solvent to the dispersion to form a solution and controlling the temperature of the solution to provide graphene form.

Description

Technical area

These This invention relates generally to a process for the reduction of graphene oxide on graphene and, in particular, a process for the reduction of graphene oxide to graphene in high boiling solvents.

background

graphs is an under development material with application potential in electrical engineering and materials science. Researchers are always trying to simpler and more efficient ways to To find graph generation. In a method of production graphene reduces graphene oxide to graphene. Graphene oxide is a layered material obtained from the oxidation of graphite and in water in the form of independent layers is dispersible. These layers can be obtained by deoxidizing the Graphenoxoxids are reduced to graphene. Typical for this Graphene layers is that they interact with each other when the reduction occurs agglomerate and thus precipitate as a solid precipitate. A target This is the uniform dispersibility of these layers maintain. In other words, agglomerate or clump in the final product should be minimized as far as possible.

at a chemical process for the deoxidation of graphene oxide Hydrazine used. Leaves hydrazine on a graphene oxide solution, this leads typically causing graphene plates to precipitate out of solution. As recent reports in the literature show, it is through careful control the pH and the hydrazine concentration possible, the Agglomerationsneigung to attenuate the graphene layers during reduction. This procedure will This is commercially unattractive that the pH is carefully adjusted and the hydrazine must be separated by means of dialysis. In addition, hydrazine is a dangerous Substance that is explosive and highly toxic. The use of hydrazine In this method means that special handling is required is. When using hydrazine, the graphene platelets also tend for extended periods of time to agglomeration or clumping. It would be desirable to have a process for the production of graphene without hazardous chemicals. A dispersion from individual graphene layers containing no lumps more desirable and possible the use of the resulting product in applications such. As transparent conductors, fillers for composite materials or polymer films.

The Thermal deoxidation is another method of deoxidation of graphene oxide layers. However, with this method, the Graphene oxide temperatures of more than 1000 ° C are exposed. In addition is this process slow and requires the use of an inert gas such. Argon. The requirement of an inert gas atmosphere and excessively high temperatures makes the production of graphene more arduous. The product of thermal Decomposition falls rather in the form of wrinkled layers than in the form of flat layers, with which Also, the commercial usefulness of the layers is limited.

Summary

One embodiment a method and a composition is a method of preparation of graphene containing the steps of dispersing graphene oxide in water to form a dispersion. The procedure further comprises adding a solvent to the dispersion, a solution to form, and control the temperature of the solution to to form dispersible graphene.

One another embodiment the method and the composition is a composition the reduced graphitic carbon and a solvent includes, wherein the solvent at least one of N-methylpyrrolidone, ethylene glycol, glycerol and dimethylpyrrolidone.

Description of the drawings

The Features of the embodiments of the present method and composition are set forth with particularity in the appended claims become. These embodiments can be best understood by the following description with the accompanying drawings, wherein in these several Figures the same reference numerals denote the same elements and wherein:

1 Figure 3 is a flow chart showing the steps involved in a first embodiment of a method of reducing graphene oxide to graphene;

2 Figure 5 is a flow chart showing the steps involved in a second embodiment of a method for reducing graphene oxide to graphene.

Detailed description

Embodiments of the present method and composition are a description of the reduction of graphene oxide to Gra phen in high-boiling solvents.

As one of ordinary skill in the art will readily understand that graphene oxide will decompose when heated to temperatures around 200 ° C to graphene. At the decay of Graphene oxide to graphene, however, it is desirable to form the graphene to keep a dispersion, making it easier in commercial Products can be used. A possibility of reduction of Graphene oxide to graphene consists in the deoxidation of graphene oxide.

graphene typically falls in the form of water-dispersible layers. The graphene oxide can be reduced to graphene by the graphene oxide layers deoxidized to obtain graphene layers. In the reduction from graphene oxide to graphene, the graphene sheets tend to clump or Agglomeration. As already mentioned, it is desirable the graphene oxide in the reduction of graphene oxide to graphene in To hold form of a dispersion.

at a method used to produce dispersible graphene layers to lead Graphene oxide is dispersed in water to form a dispersion to give individual graphene oxide layers, and then the dispersion with a high-boiling solvent added to a solution to build. The high-boiling solvent can a solvent with a boiling point of about 200 ° C or higher be. As the solvent has a high boiling point, the solution may be without evaporation of the solvent while The deoxidation of the graphene oxide are heated to about 200 ° C, so that finally the dispersible graphene is obtained. A more detailed description of this Method follows.

In 1 FIG. 10 is a flowchart showing a first embodiment. FIG 100 of a process for the reduction of graphene oxide to graphene. In step 110 a dispersion is generated. The dispersion may comprise graphene oxide which is dispersed by sonication in water. Sonication as described herein may involve inducing cavitation by application of ultrasound for the purpose of achieving dispersion. The graphene oxide may be in the form of water-dispersible layers. The dispersion of the graphene oxide by sonication may lead to a dispersion which consists of individual graphene oxide platelets. The individual graphene oxide platelets can form a more stable dispersion. A stable graphene oxide dispersion makes it easier to form a graphene dispersion. The ratio of water to graphene oxide in the dispersion may be about one milligram of graphene oxide to about one milliliter of water.

The dispersion 120 may be mixed with a solvent to form a solution. The solvent may be a water-miscible solvent such as N-methylpyrrolidone, ethylene glycol, glycerol, dimethylpyrrolidone, acetone, tetrahydrofuran, acetonitrile, dimethylformamide, an amine or an alcohol. The amount of solvent added to the dispersion may be about the same as the amount of the dispersion. Thus, if the dispersion consists of one milliliter of water and one milligram of graphene oxide, then the dispersion may be mixed with a volume or amount of solvent corresponding to about one milliliter of water and one milligram of graphene oxide. The solution may now comprise a mixture having a value of about half graphene oxide / water dispersion and one half high boiling solvent.

The solution can be gradually heated to about 200 ° C ( 130 ). In some embodiments, the solution may be heated in an autoclave or in a high pressure chamber. As one of ordinary skill in the art readily understands, heating the solution in a pressurized environment may increase the boiling point of the solution with the solvent. Thus, the boiling point of the solution can reach or exceed 200 ° C. When the solution is heated in a pressurized environment, a solvent having a boiling point slightly below 200 ° C may be used.

Upon heating the solution, the solution can be stirred. With the heating of the solution, the water can be removed by evaporation from the solution. As expected, the temperature of the solution increases with the pull of the water. As the temperature increases, the graphene oxide is deoxidized. When the temperature of the solution reaches about 200 ° C, a reduction may form. Upon heating the solution, the surface of the graphene oxide can be functionalized, which may cause the platelets in the final product to clump less. In one embodiment, the temperature may be maintained at about 200 ° C for a period of time ( 140 ) to support the functionalization of the reduction. In some embodiments, the temperature may be held for only one hour. In other embodiments, the temperature may be maintained for as long as twenty-four hours. In other embodiments, the temperature of the solution may be held for only a moment when the temperature reaches about 200 ° C to form a reduction.

For cooling, the heater can be removed from the reduction batch. Since the reduction approach still contain solvents If desired, the reduction batch can be purified to remove as much of the remaining solvent as possible ( 150 ). The purification of the reduction batch may comprise filtering the reduction batch. The reduction batch can also be redispersed in acetone and centrifuged as part of the purification process. The final result of the cleaning process can be a solid. The solid may be graphene containing trace amounts of the solvent.

In 2 FIG. 4 is a flowchart showing a second embodiment. FIG 200 of the process for the reduction of graphene oxide to graphene. In step 210 the process produces a dispersion. The dispersion may comprise water-dispersible graphene oxide layers which are dispersed in water by sonication. The ratio of water to graphene oxide may be about two milligrams of graphene oxide to about one milliliter of water.

The dispersion 220 may be mixed with a solvent to form a solution. The solvent may be a water-miscible solvent such as N-methylpyrrolidone, ethylene glycol, glycerol, dimethylpyrrolidone, acetone, tetrahydrofuran, acetonitrile, dimethylformamide, an amine or an alcohol. The amount of solvent added to the dispersion may be about half the amount of the dispersion. Thus, if the dispersion consists of about two milligrams of graphene oxide and about one milliliter of water, the amount of solvent added to the dispersion may be about one-half the volume or amount of about two milligrams of graphene and about one milligram of water.

The solution can be heated gradually ( 230 ). In some embodiments, the solution may be heated in an autoclave or in a high pressure chamber. As one of ordinary skill in the art readily understands, heating the solution in a pressurized environment may increase the boiling point of the solution with the solvent. Thus, the boiling point of the solution can reach or exceed 200 ° C. When the solution is heated in a pressurized environment, a solvent having a boiling point slightly below 200 ° C may be used.

At the Heating the solution The solution can be stirred. With heating and stirring the solution can the water from the solution evaporate. Just as the water evaporates from the solution, a lot can happen solvent be added to the dispersion, which is about the amount of evaporated Water corresponds. The steps of gradually heating the solution, the stirring the solution and the addition of solvent to replace the evaporated water can continue until the Temperature of the solution about 200 ° C reached. When the temperature reaches about 200 ° C, there may be a reduction form. By heating the solution, the surface of the Graphenoxoxid be functionalized, which may cause the platelets in the Less clumped end product. In one embodiment, the temperature for a while at 200 ° C held to support the functionalization of the reduction. In some embodiments It may be that the temperature is kept for only one hour. In other embodiments can the temperature over to be held for as long as twenty-four hours. In further embodiments It may be that the temperature of the solution is only a moment is held, as soon as the temperature reaches about 200 ° C to a reduction train.

For cooling, the heater can be removed from the reduction batch. The cooled reduction batch can be purified ( 260 ). The purification of the reduction batch may comprise filtering the reduction batch to remove the solvent remaining in the reduction batch. The reduction batch can be redispersed in acetone and centrifuged to recover a solid. The solid may be graphene containing trace amounts of the solvent.

The present methods and composition are not limited to the specific details of the embodiments shown, and There are also other modifications and applications conceivable. There may be certain others amendments made on the embodiments described above without departing from the spirit and scope of the present process and the present composition. The object The above illustration is therefore intended to be illustrative and not restrictive Senses are understood.

Claims (21)

Process for producing graphene, comprising the steps: Dispersing graphene oxide in water to form a dispersion to build; Add a solvent to the dispersion, to a solution to build; and Check the temperature of the solution to To form graphene. The method of claim 1, wherein the dispersing of the graphene oxide in water further dispersing the graphene oxide in water by sonication. The method of claim 1, wherein the Disper a ratio of about one milligram of graphene oxide to about one milliliter of water. The method of claim 1, wherein the solvent a water-miscible solvent is. The method of claim 4, wherein the water-miscible solvent at least one of N-methylpyrrolidone, ethylene glycol, glycerol, Dimethylpyrrolidone, acetone, tetrahydrofuran, acetonitrile, dimethylformamide, an amine and an alcohol. The method of claim 1, wherein the addition of the solvent for dispersion, further adding an amount of solvent includes, which corresponds approximately to the amount of the dispersion. The method of claim 1, wherein said controlling the temperature of the solution further heating the solution at about 200 ° C includes to form a reduction. The method of claim 7, further comprising the step of stirring the solution while the solution is heated. The method of claim 7, further comprising the step of maintaining the temperature of the solution at about 200 ° C. The method of claim 7, further comprising keeping the temperature of the solution as soon as possible the water from the solution has evaporated. The method of claim 7, further comprising heating the solution in at least one of autoclave and high pressure chamber. The method of claim 7, further comprising cleaning the reduction batch. The method of claim 12, wherein cleaning the The reduction approach further comprises the following steps: dispersing of the reduction batch in acetone to form a dispersed reduction batch to build; Centrifuging the dispersed reduction batch; and Filter the dispersed reduction batch in acetone. The method of claim 1, wherein the graphene oxide is dispersed by sonication in water and the dispersion relationship from about two milligrams of graphene oxide to about one milliliter of water includes. The method of claim 14, wherein the solvent a water-miscible solvent is at least one of N-methylpyrrolidone, ethylene glycol, Glycerol, dimethylpyrrolidone, acetone, tetrahydrofuran, acetonitrile, Dimethylformamide, an amine and an alcohol. The method of claim 14, wherein the addition of the solvent for dispersion, further adding an amount of solvent that covers about half the amount of dispersion corresponds. The method of claim 14, wherein said controlling the temperature of the solution further comprises the following steps: Heating the solution up about 200 ° C; discontinuous Add the solvent to the solution as the water evaporates, so the amount of added solvent corresponds approximately to the amount of evaporated water; Stirring the Solution; and Holding the temperature of the solution to form a reduction, once all the water has evaporated. The method of claim 17, wherein controlling the temperature of the solution further heating the solution in an autoclave or a high pressure chamber. The method of claim 18, further comprising cleaning the reduction batch. The method of claim 19, wherein the cleaning of the The reduction approach further comprises the following steps: dispersing of the reduction batch in acetone to form a dispersed reduction batch to build; Centrifuging the dispersed reduction batch; and Filter the dispersed reduction batch in acetone. Graphene composition comprising reduced graphitic Carbon and a water-miscible solvent, the with Water-miscible solvents at least one of N-methylpyrrolidone, ethylene glycol, glycerol, Dimethylpyrrolidone, acetone, tetrahydrofuran, acetonitrile, dimethylformamide, an amine and an alcohol.